操作JPEG图像

使用ExifData类读取和修改Jpeg EXIF标签

几乎所有数字相机（包括智能手机）、扫描仪和其他处理图像的系统都会保存带有EXIF（可交换图像文件）信息的图像。相机设置和场景信息由相机记录到图像文件中。 EXIF数据还包括快门速度、拍摄日期和时间、焦距、曝光补偿、测光模式以及是否使用了闪光灯等信息。Aspose.Imaging APIs已经可以轻松简单地从给定图像中提取EXIF信息。开发人员也可以根据自己的需求向图像中写入EXIF数据或修改现有信息。Aspose.PSD为读取、写入和修改EXIF数据提供了ExifData类，而Aspose.PSD.Exif.Enums命名空间包含了在此过程中使用的相关枚举。

读取EXIF数据

Aspose.PSD APIs提供了从给定图像中读取EXIF数据的方法。下面提供的步骤说明了使用ExifData类从图像中读取EXIF信息的用法。

使用工厂方法Load加载PSD图像。
在PSD资源中查找Jpeg缩略图。
提取ExifData类的实例。

提取所需信息并将其写入控制台。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "1280px-Zebras_Serengeti.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Extract exif data and print to the console.
	var exif = ((ThumbnailResource)resource).JpegOptions.ExifData;
	if (exif != null)
	{
	Type type = exif.GetType();
	PropertyInfo[] properties = type.GetProperties();
	foreach (PropertyInfo property in properties)
	{
	Console.WriteLine(property.Name + ":" + property.GetValue(exif, null));
	}
	}
	}
	}
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-ReadAllEXIFTags-ReadAllEXIFTags.cs hosted with ❤ by GitHub

或者，开发人员还可以使用以下代码片段获取特定信息。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "1280px-Zebras_Serengeti.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Extract exif data and print to the console.
	var exif = ((ThumbnailResource)resource).JpegOptions.ExifData;
	if (exif != null)
	{
	Console.WriteLine("Exif WhiteBalance: " + exif.WhiteBalance);
	Console.WriteLine("Exif PixelXDimension: " + exif.PixelXDimension);
	Console.WriteLine("Exif PixelYDimension: " + exif.PixelYDimension);
	Console.WriteLine("Exif ISOSpeed: " + exif.ISOSpeed);
	Console.WriteLine("Exif FocalLength: " + exif.FocalLength);
	}
	}
	}
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-ReadSpecificEXIFTagsInformation-ReadSpecificEXIFTagsInformation.cs hosted with ❤ by GitHub

写入和修改EXIF数据

使用Aspose.PSD APIs，开发人员可以写入新的EXIF信息并修改图像的现有EXIF数据。写入和修改两个过程都需要加载图像并将EXIF数据获取到ExifData类的实例中。然后可以访问ExifData类公开的属性，根据需要进行设置。请注意，用于操作的图像应为通常为PSD缩略图的Jpeg或Tiff图像。演示如何使用的示例代码如下：

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "sample.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Extract exif data and print to the console.
	var exif = ((ThumbnailResource)resource).JpegOptions.ExifData;
	if (exif != null)
	{
	// Set LensMake, WhiteBalance, Flash information Save the image
	exif.LensMake = "Sony";
	exif.WhiteBalance = ExifWhiteBalance.Auto;
	exif.Flash = ExifFlash.Fired;
	}
	}
	}

	image.Save(dataDir + "aspose_out.psd");
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-WritingAndModifyingEXIFData-WritingAndModifyingEXIFData.cs hosted with ❤ by GitHub

从PSD资源中提取缩略图

缩略图是图片的缩小版，用于显示图片的重要部分而不是整个画面。一些图像文件（特别是用数码相机拍摄的图像）在文件中嵌入了缩略图像。Aspose.PSD API允许您提取PSD资源缩略图并将其单独存储到磁盘上。缩略资源包含ExifData.缩略图属性，可检索缩略图数据。下面提供的代码片段演示了如何使用它。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "1280px-Zebras_Serengeti.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Extract thumbnail data and store it as a separate image file.
	var thumbnail = (ThumbnailResource)resource;
	var data = ((ThumbnailResource)resource).ThumbnailArgb32Data;
	using (PsdImage extractedThumnailImage = new PsdImage(thumbnail.Width, thumbnail.Height))
	{
	extractedThumnailImage.SaveArgb32Pixels(extractedThumnailImage.Bounds, data);
	extractedThumnailImage.Save(dataDir + "extracted_thumbnail.jpg", new JpegOptions());
	}
	}
	}
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-ExtractThumbnailFromPSD-ExtractThumbnailFromPSD.cs hosted with ❤ by GitHub

使用上述讨论的方法将缩略图存储为其他支持的文件格式。如果要将缩略图数据导出到其他图像格式，例如BMP和PNG，请使用其他图像导出选项。

从JFIF段中提取缩略图

还可以从PSD缩略资源的ExifData或JFIF段中提取缩略图。以下代码显示如何从JFIF或ExifData段中执行缩略图数据的提取：

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "1280px-Zebras_Serengeti.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Extract thumbnail data and store it as a separate image file.
	var thumbnail = (ThumbnailResource)resource;
	var data = ((ThumbnailResource)resource).ThumbnailArgb32Data;
	using (PsdImage extractedThumnailImage = new PsdImage(thumbnail.Width, thumbnail.Height))
	{
	extractedThumnailImage.SaveArgb32Pixels(extractedThumnailImage.Bounds, data);
	extractedThumnailImage.Save(dataDir + "extracted_thumbnail.jpg", new JpegOptions());
	}
	}
	}
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-ExtractThumbnailFromPSD-ExtractThumbnailFromPSD.cs hosted with ❤ by GitHub

使用上述讨论的方法将缩略图存储为其他支持的文件格式。如果要将缩略图数据导出到其他图像格式，例如BMP和PNG，请使用其他图像导出选项。

向JFIF段添加缩略图

下面的代码片段演示了如何使用JFIF。缩略图属性将缩略图添加到加载的PSD图像的JFIF段中。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "aspose_out.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Adjust thumbnail data.
	var thumbnail = (ThumbnailResource)resource;
	var jfifData = new FileFormats.Jpeg.JFIFData();
	var thumbnailImage = new PsdImage(100, 100);
	try
	{
	// Fill thumbnail data.
	int[] pixels = new int[thumbnailImage.Width * thumbnailImage.Height];
	for (int i = 0; i < pixels.Length; i++)
	{
	pixels[i] = i;
	}

	// Assign thumbnail data.
	thumbnailImage.SaveArgb32Pixels(thumbnailImage.Bounds, pixels);
	jfifData.Thumbnail = thumbnailImage;
	jfifData.XDensity = 1;
	jfifData.YDensity = 1;
	thumbnail.JpegOptions.Jfif = jfifData;
	}
	catch
	{
	thumbnailImage.Dispose();
	throw;
	}
	}
	}

	image.Save();

	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-AddThumbnailToJFIFSegment-AddThumbnailToJFIFSegment.cs hosted with ❤ by GitHub

缩略图与其他段数据一起，由于JPEG格式的规范，不能超过65545字节。如果要将大图像设置为缩略图，可能会引发异常。

向EXIF段添加缩略图

下面的代码片段演示了如何使用ExifData.Thumbnail属性将缩略图添加到加载的PSD图像的EXIF段中。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "aspose_out.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Adjust thumbnail data.
	var thumbnail = (ThumbnailResource)resource;
	var exifData = new JpegExifData();
	var thumbnailImage = new PsdImage(100, 100);
	try
	{
	// Fill thumbnail data.
	int[] pixels = new int[thumbnailImage.Width * thumbnailImage.Height];
	for (int i = 0; i < pixels.Length; i++)
	{
	pixels[i] = i;
	}

	// Assign thumbnail data.
	thumbnailImage.SaveArgb32Pixels(thumbnailImage.Bounds, pixels);
	exifData.Thumbnail = thumbnailImage;
	thumbnail.JpegOptions.ExifData = exifData;
	}
	catch
	{
	thumbnailImage.Dispose();
	throw;
	}
	}
	}

	image.Save();

	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-AddThumbnailToEXIFSegment-AddThumbnailToEXIFSegment.cs hosted with ❤ by GitHub

在这种情况下，Aspose.PSD API无法估计缩略图大小，但可以检查整个EXIF数据段的大小。这不能超过65535字节。

使用JpegExifData类读取和修改Jpeg EXIF标签

Aspose.PSD APIs提供了专门用于Jpeg图像格式的JpegExifData类来检索和更新EXIF信息。本文演示了如何使用JpegExifData类实现相同的效果。Aspose.PSD.Exif.JpegExifData类充当Jpeg图像的EXIF数据容器，提供了检索标准Jpeg EXIF标签的方法，如下所示：

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "aspose_out.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Adjust thumbnail data.
	var thumbnail = (ThumbnailResource)resource;
	var exifData = new JpegExifData();
	var thumbnailImage = new PsdImage(100, 100);
	try
	{
	// Fill thumbnail data.
	int[] pixels = new int[thumbnailImage.Width * thumbnailImage.Height];
	for (int i = 0; i < pixels.Length; i++)
	{
	pixels[i] = i;
	}

	// Assign thumbnail data.
	thumbnailImage.SaveArgb32Pixels(thumbnailImage.Bounds, pixels);
	exifData.Thumbnail = thumbnailImage;
	thumbnail.JpegOptions.ExifData = exifData;
	}
	catch
	{
	thumbnailImage.Dispose();
	throw;
	}
	}
	}

	image.Save();

	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-AddThumbnailToEXIFSegment-AddThumbnailToEXIFSegment.cs hosted with ❤ by GitHub

完整的EXIF标签列表

上面的代码片段使用Aspose.PSD.Exif.JpegExifData类提供的属性读取了几个EXIF标签。这些属性的完整列表在此处可用。以下代码将使用System.Reflection.PropertyInfo类读取所有EXIF标签。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	using (PsdImage image = (PsdImage)Image.Load(dataDir + "1280px-Zebras_Serengeti.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Extract thumbnail data and store it as a separate image file.
	var thumbnail = (ThumbnailResource)resource;
	var exifData = thumbnail.JpegOptions.ExifData;
	if (exifData != null)
	{
	Type type = exifData.GetType();
	PropertyInfo[] properties = type.GetProperties();
	foreach (PropertyInfo property in properties)
	{
	Console.WriteLine(property.Name + ":" + property.GetValue(exifData, null));
	}
	}
	}
	}
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-ReadAllEXIFTagList-ReadAllEXIFTagList.cs hosted with ❤ by GitHub

自动校正JPEG图像的方向

照片可以是使用相机旋转90°、180°、270°或无旋转（正常方向）拍摄的。大多数数字相机以EXIF标签的形式将方向信息存储在JEPG图像的图像数据中。此信息可用于在图像上执行自动旋转以更正方向。Aspose.PSD APIs为JpegImage类提供了AutoRotate方法，用于自动校正JPEG图像的方向。以下是如何使用Aspose.PSD for .NET API的AutoRotate方法的方法。

支持使用CMYK和YCCK的JPEG-LS

Aspose.PSD for .NET API支持CMYK和YCCK颜色模型与JPEG-LS。下面的代码片段演示了如何使用JPEG-LS的支持。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "PsdImage.psd"))
	{
	JpegOptions options = new JpegOptions();
	//Just replace one line given below in examples to use YCCK instead of CMYK
	//options.ColorType = JpegCompressionColorMode.Cmyk;
	options.ColorType = JpegCompressionColorMode.Cmyk;
	options.CompressionType = JpegCompressionMode.JpegLs;

	// The default profiles will be used.
	options.RgbColorProfile = null;
	options.CmykColorProfile = null;

	image.Save(dataDir + "output.jpg", options);
	}

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "PsdImage.psd"))
	{
	JpegOptions options = new JpegOptions();
	//Just replace one line given below in examples to use YCCK instead of CMYK
	//options.ColorType = JpegCompressionColorMode.Cmyk;
	options.ColorType = JpegCompressionColorMode.Cmyk;
	options.CompressionType = JpegCompressionMode.Lossless;

	// The default profiles will be used.
	options.RgbColorProfile = null;
	options.CmykColorProfile = null;

	image.Save(dataDir + "output2.jpg", options);
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-SupportForJPEG_LSWithCMYK-SupportForJPEG_LSWithCMYK.cs hosted with ❤ by GitHub

支持JPEG-LS图像中的每个样本2-7位

Aspose.PSD for .NET API支持每个样本2-7位的JPEG-LS图像。下面的代码片段演示了如何使用JPEG-LS的支持。

为JPEG图像设置ColorType和CompressionType

Aspose.PSD for .NET API支持颜色类型和压缩类型，并将其设置为JPEG图像的灰度和渐进。下面的代码片段演示了如何使用该支持。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "PsdImage.psd"))
	{
	JpegOptions options = new JpegOptions();
	options.ColorType = JpegCompressionColorMode.Grayscale;
	options.CompressionType = JpegCompressionMode.Progressive;

	image.Save(dataDir + "ColorTypeAndCompressionType_output.jpg", options);
	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-ColorTypeAndCompressionType-ColorTypeAndCompressionType.cs hosted with ❤ by GitHub

下面的代码片段演示了如何使用ExifData.Thumbnail属性向加载的PSD图像的EXIF段添加缩略图。

	// For complete examples and data files, please go to https://github.com/aspose-psd/Aspose.PSD-for-.NET

	// Load PSD image.
	using (PsdImage image = (PsdImage)Image.Load(dataDir + "aspose_out.psd"))
	{
	// Iterate over resources.
	foreach (var resource in image.ImageResources)
	{
	// Find thumbnail resource. Typically they are in the Jpeg file format.
	if (resource is ThumbnailResource \|\| resource is Thumbnail4Resource)
	{
	// Adjust thumbnail data.
	var thumbnail = (ThumbnailResource)resource;
	var exifData = new JpegExifData();
	var thumbnailImage = new PsdImage(100, 100);
	try
	{
	// Fill thumbnail data.
	int[] pixels = new int[thumbnailImage.Width * thumbnailImage.Height];
	for (int i = 0; i < pixels.Length; i++)
	{
	pixels[i] = i;
	}

	// Assign thumbnail data.
	thumbnailImage.SaveArgb32Pixels(thumbnailImage.Bounds, pixels);
	exifData.Thumbnail = thumbnailImage;
	thumbnail.JpegOptions.ExifData = exifData;
	}
	catch
	{
	thumbnailImage.Dispose();
	throw;
	}
	}
	}

	image.Save();

	}

view raw Examples-CSharp-Aspose-ModifyingAndConvertingImages-JPEG-AddThumbnailToEXIFSegment-AddThumbnailToEXIFSegment.cs hosted with ❤ by GitHub

在这种情况下，Aspose.PSD API无法估算缩略图的大小，但可以检查整个EXIF数据段的大小。这不能超过65535字节。

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